The present invention is related to Japanese patent application No. Hei. 11-207669, filed Jul. 22, 1999; No. 2000-68733, filed Mar. 13, 2000, the contents of which are incorporated herein by reference.
The present invention relates generally to a suction apparatus for an internal combustion engine, and more particularly, to a suction apparatus for an internal combustion engine.
Conventionally, there is known a technique for preventing operational defects due to freezing of a throttle body of an internal combustion engine. In such techniques, generally, a warm water passage is provided for circulating engine-cooling water in the vicinity of a suction passage in the throttle body. The cooling water heated by the engine flows through that warm water passage, thereby heating the throttle body and preventing the throttle body from freezing.
For example, according to the throttle body disclosed in JP-A-8-135506, by shaping a partition wall (used for partitioning a suction passage from a warm water passage) as a thin wall and reinforcing this partition wall with a rib, the heat conduction efficiency of the throttle body is increased, thereby preventing freezing.
Also, JP-A-6-117328 provides a throttle body having no such warm water passage. Here, a throttle body and a cylinder block are connected to each other by a heat pipe. Latent heat from an operational liquid filled within the heat pipe is utilized to conduct heat from the cylinder block and prevent freezing of the throttle body.
However, in the throttle body according to JP-A-8-135506, piping must be used for guiding the engine-cooling water into the throttle body and circulating the engine-cooling water so that the engine-cooling water returns to an engine main body via the throttle body. This type of piping necessitates the use of a complex structure for conducting a large amount of heat from the engine main body to the throttle body. Accordingly, the space needed for installing the throttle body is large. Also, this design has increased weight, complex assembly, and increased manufacturing cost.
On the other hand, in JP-A-6-117328, the end portion of the heat-radiating side of the heat pipe must be raised higher than the end portion of a heat input side. Moreover, the heat pipe must be installed in this state. Because of the space within the engine room, the throttle body is installed higher than the cylinder block and these two elements cannot be connected together by a heat pipe. Also, since since leakage of the operational liquid must be prohibited, the manufacturing cost increases. The present invention was developed in light of these and other drawbacks.
It is therefore an object of the present invention to provide a suction apparatus for an internal combustion engine which is small, prevents freezing of the throttle body, and reduces the number of parts and the number of assembly steps.
It is another object of the present invention to provide a suction apparatus having a simple structure capable of preventing vibrations.
To achieve these and other objects, the present invention provides a suction apparatus for an internal combustion engine having a vent hole formed in the head cover. A heat conduction portion, provided on the throttle body, is inserted from the external space on the anti combustion chamber side into the vent hole. The heat conduction portion is inserted into the internal space of the head cover that contains a cam for driving the suction valve or exhaust valve. Accordingly, heat within the internal space of the head cover easily conducts to the throttle body and throttle valve. As a result, freezing of the throttle valve is prevented. For example, it is possible to construct the heat conduction portion using a formed metal material having high heat conductivity. Or a resin material may be used which contains such metal material.
In another aspect of the present invention, the heat conduction portion is formed integrally with the throttle body forming therein the suction passage. Since the throttle body serves as the partition wall of the internal space of the head cover, it is possible to directly heat the throttle body with the heat of the internal space of the head cover.
In another aspect of the present invention, the throttle body has the idle speed control portion forming therein the bypass passage bypassing the throttle valve, and the heat conduction portion is provided on this idle speed control portion.
In another aspect of the present invention, since the heat conduction portion is formed into a hollow-cylindrical configuration, the wall portion of the suction passage or bypass passage becomes the partition wall of the internal space of the head.
In another aspect of the present invention, the heat conduction portion is constructed by causing one end of the throttle shaft to protrude outside the throttle body. Since it is possible to construct the heat conduction portion without using new parts, the number of parts is reduced. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.